Ribonucleotide reductase (RNR) from Escherichia coli catalyzes the conversion of nucleotides to deoxynucleotides and is composed of two homodimeric subunits: R1 and R2. We have performed several experiments with this protein over the past three years. Initially, we obtained a 140 GHz spectrum which revealed a well resolved g-anisotropy and hyperfine couplings to the 3,5-aromatic protons as well as the P-CH2-The simulated 140 GHz lineshape is in excellent agreement with the experimental spectrum and a comparison of the 9 and 140 GHz spectra shows the advantage of recording this line shape at high field.